Monobaths for photographic processing



United States Patent 3,512,980 MONOBATHS FOR PHOTOGRAPHIC PROCESSING Christopher Lucas, Eatontown, NJ., assignor to the United States of America as represented by the Secretary of the Army No Drawing. Filed Nov. 17, 1966, Ser. No. 595,272

Int. Cl. G03c 5/38 US. Cl. 96-61 2 Claims ABSTRACT OF THE DISCLOSURE An aqueous monobath containing thioglycollic acid, potassium hydroxide and hydroquinone in particular amounts is used to process a photographic emulsion in four to five seconds at about 120 F.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to monobaths for rapid high temperature negative photographic processing and to a method of photographic processing using the monobaths.

Heretofore, attempts to rapidly process suitable negative materials at high temperatures, that is, at about 120 F., have generally involved the use of monobaths containing substantial amounts of sodium thiosulfate. The problem with most sodium thiosulfate formulas, however, is that they usually sludge and plate silver on the film. Moreover, these monobaths require a processing time of at least 12 seconds at about 120 F. which is not sufiiciently rapid for use in certain applications such as in a near real time aerial reconnaissance phototransmission system, which includes a camera, processor, and scanner. In that system, scanning produces an electronic signal from the processed image that is suitable for transmission to a ground receiver. Very rapid processing of five seconds or less is required to reduce exposure to scan times.

A general object of this invention is to provide a method of processing a photographic negative at a temperature about 120 F. in five seconds or less without plating silver onto the film. A further object of the invention is to provide such a method of photographic processing wherein the processed negative is characterized by a resolution of approximately 70 lines per millimeter, an exposure index of at least 25, a gamma of approximately 1.0, and a base plus fog density of approximately 0.25. A still further object of the invention is to provide a monobath for use in the method of photographic processing. I I

It has now been found that the foregoing objectives can be attained by a method involving the continuous and rapid agitation of the photographic emulsion for four to five seconds at about 120 F. in a particular type monobath formula. Particularly, the monobath comprises the following materials with their respective amounts.

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MONOBATH Material: Amount, about- Thioglycollic acid ..cc 45-55 Potassium hydroxide grams 130-175 Hydroquinone do 40-90 Water to make 1 liter.

To increase film speed, 5 grams of l-phenyl-El-pyrazolidone may be added to the monobath. Similarly, to improve resistance to aerial oxidation, 5 to 25 grams of potassium arsenite may be added to the monobath. A particularly desirable monobath is found to consist of the following materials with their respective amounts.

MONOBATH Material: Amount Thioglycollic acid cc 50 Potassium hydroxide grams 145 l-phenyl-B-pyrazolidone do 5 Hydroquinone do 50 Potassium arsenite do 20 Water to make 1 liter.

The latter monobath is resistant to aerial oxidation and has a high exhaustion capacity. That is, 2 gallons of monobath is sufficient for 500 feet of millimeter film.

When suitable film is processed according to the method of the invention using the preferred monobath set forth above, a resolution of 70 lines per millimeter is obtained with no silver plating on the film. The processed film is further characterized by an exposure index of 50, a gamma of 0.84, and a base plus fog density of 0.28. If desired, a very brief water rinse (approximately /2 second) can be used to wash the chemicals from the surface of the emulsion and prevent chemical crystallization after the film is dried.

Suitable film for use in the invention are panchromatic, hardened, thin gelatino silver iodobromide emulsions that can Withstand temperatures as high as 130 C.

The foregoing description is to be considered as illustrative of the invention and not in limitation thereof.

What is claimed is:

1. A monobath for processing a photographic negative at a temperature about F. in four to five seconds so that the processed negative will be characterized by an exposure index of at least 25, a resolution of approximately 70 lines per millimeter, a gamma of approximately 0.25, said monobath consisting-of the following materials with their respective amounts:

Material: Amount, about- Thioglycollic acid cc 45-55 Potassium hydroxide grams.. -175 Hydroquinone do 40-90 Water to make 1 liter.

2. A method of rapidly processing a photographic negative so that the processed negative will be characterized by an exposure index of at least 25, a resolution of approximately 70 lines per millimeter, a gamma of approximately 1.0, and a base plus fog density of approximately 0.25 comprising continuously and rapidly agitating the photographic emulsion for four to five seconds 3 4 at about 120 in a monobat11 consisting of the follow- OTHER REFERENCES ing materials with their respectlve amounts: v V v Photo & Engineering, vol. 5, No 4, Ju1y August Material: Amount, about- 1961, pp. 198-203.

Thioglycollic acid cc 45-55 British Journal of Photography, Jan. 23, 1959, pp. Potassium hydroxide grams 130-175 5 Hydroquinone do 40-90 Water to ak 1 lit NORMAN G. TORCHIN, Primary Examiner References Cited M. F. KELLEY, Asslstant Examlner 10 US. Cl. X.R.

UNITED STATES PATENTS 3,050,392 8/1962 Eerde 9666.5 96-48 3,255,008 6/1966 Teflt. 

